Pump Example

See the pumps section for the necessary background to solve this problem.

The Problem

A pump is installed to fill an open water storage tank (elevation at the bottom of the tank is 200 ft asl) from a 70 degrees F reservoir (elevation at the piping outlet is 100 ft asl). The pump manufacturer has specified a minimum Net Positive Suction Head Required of 10 ft when pumping at 900 gpm. The six-inch Schedule 40 steel piping that connects the pump between the reservoir and the storage tank is 1000 ft long, contains six flanged 90 degree elbows, is connected to the reservoir at its bottom elevation, and discharges at the top of the upper strorage tank. If the depth of the water in the upper storage tank is 20 ft, what is the minimum depth of reservoir to prevent cavitation when the atmospheric pressure is 13 psi and the discharge of the pump is 900 gpm? Assume the Re of the flow is 100,000.